Doors having compression molded door skins are well known in the art. Attempts have been made to provide a textured pattern on the exterior of the door skin to simulate the grain of natural wood. One such attempt provides a printed wood grain pattern on the door skin. However, the printed pattern has no depth or texture, as found in natural wood. Furthermore, the print ink often fails to provide for crisp wood grain lines, and varying tones.
Another attempt to simulate a natural wood grain pattern in the exterior surface of the door skin provides for transferring a photographic image of the grain pattern onto an embossing plate, by an etching process, to form a lower surface and raised lines or ridges extending from the lower surface of the metal plate. Etching is a process whereby areas of a metal plate are covered with an acid resistant ground and an acid or mordant solution is applied to the plate. The areas that have no resistant ground are eaten away by the acid. An image or pattern is etched into the metal plate that then has a lower surface, and raised portions extending from the lower surface. The resistant ground, or “resist”, controls where and how the acid eats into the metal plate. Chromed steel, copper and zinc are three most common metals used for etching plates. Chromed steel is the hardest of the three metals, and will not wear down as quickly as non-steel plates after repeated embossing.
Different acids are necessary for etching different metals. In addition, there are different resists and ways of applying the resists. There are also various ways to expose the metal to the acid after the resist has been applied so that tone and texture can be created. Acid treatment of the plate then etches out the uncoated metal, creating a raised textured surface in the embossing plate. Raised ridges, or lines, are created by etching into the plate around lines of protective resist. The acid then eats away at the metal plate, leaving raised ridges that were protected by the resist. The resulting structure creates an illusion of wood grains. The depth of the etch into the metal is controlled by the width of the corresponding line of resist that is removed.
Conventional etched plates may be used as an embossing plate, pressing the etched image or pattern into a substrate. As known in the art, the substrate is subjected to selected amounts of heat, pressure and time during embossing. When embossing a material used to form a door skin having a wood grain pattern, the etched embossing plate is pressed into the material to provide bundles of wood ticks that form the grain pattern on the resulting door skin surface. A wood grain pattern is a cluster or bundle of spaced, raised lines, or “ticks”, which extend in a pattern simulating the appearance of wood. The ticks must be carefully spaced to simulate a natural wood grain. During etching, it is often difficult to achieve clear, crisp wood ticks. If the tick is too narrow, the acid may eat into the sides of the tick, and may completely destroy the tick. As such, conventional etched plates having wood grain patterns do not emboss highly realistic wood ticks. In addition, such conventional etched plates often have sharp edges on the outer surfaces of the ticks, and undercuts near the lower portions of the plate due to the nature of the etching process. As the acid eats into the metal plate, grooves are cut therein. However, the acid also eats into the sides of ticks (separated by the groove), especially near the base of the groove. This is commonly known as undercutting, a phenomenon well known in the field of etching. The resulting ticks fail to simulate the soft, flowing appearance of natural wood ticks.
In addition, conventional door skins with embossed wood grain patterns fail to capture the subtle wood tone variations found in natural wood. Natural wood includes not only wood ticks, but varying background tones as well. Conventional embossing plates and molded die sets used to form door skins with wood grain patterns fail to capture both naturally appearing wood ticks and wood tones. If the door skin surface is stained, it does not appear realistic. As commonly known in the art, stains include a dye or pigment in solution, and are generally used to color a wood by penetrating the wood surface. As such, the natural wood tones and ticks may be enhanced or colored, without covering the wood surface textures and tones, as with paint. Stains do not penetrate the surface of a synthetic door skin in the same manner as natural wood. Therefore, attempts to stain a door skin for purposes of enhancing tones and ticks is a difficult process for a typical consumer. The stain may not simply be applied with a brush or rag, and the excess wiped off, as can be done with natural wood. Rather, multiple applications of stain are generally required, which must then be selectively removed by hand. This technique often requires a professional or one experienced in staining in order to capture a realistic wood appearance. Alternatively, portions of the door skin surface may be highlighted by spray gun application of the stain, or other shading material. Even if the stain is carefully applied in specific areas, the resulting tones and wood ticks may appear splotchy and unrealistic. Thus, it is difficult to achieve the desired tonal variations.
Therefore, there is a need for a molded door skin having a wood grain pattern that may be easily stained, and that precisely captures both the wood ticks and wood tones found in natural wood grain.